This invention relates to an optical disk recording device and, more particularly, to an optical disk recording device in Which data is recorded by projecting laser pulse on a disk on which time information or address information used for writing is pre-recorded while controlling drive of a spindle for rotating the disk by using the information for writing.
Known in the art of a write once read mostly optical disk,is a CD-WO (Compact Disc - Write Once) disk. In a CD-WO disk is recorded a previously wobbled ATIP (Absolute Time In Pre-groove) data before data is recorded. The ATIP data includes a position detection synchronizing signal (so called ATIP Sync), time data representing absolute time (minute, second and frame) at each position on the disk and CRC data.
In the CD-WO system, a single optical pickup serves both as a recording optical pickup and a reproducing optical pickup and, therefore, ATIP data is read out simultaneously with recording of data on the disk. A clock is generated in synchronism with the read out ATIP data and a spindle control is performed to obtain a desired disk rotation speed on the basis of this clock. This clock has, as shown in FIG. 2, a frequency of 6.3 kHz and is determined to synchronize with the ATIP Sinc at every 84 clocks. For generating this clock, a PLL circuit is normally employed.
According to the data recording method using the PLL, by locking the PLL at the start of recording and thereby controlling a spindle, phase difference between read out ATIP data and recorded data is held within +180 degrees. Actually, however, a phase difference exceeding 180 degrees is often produced due to various causes including vibration of the spindle, dust and noise and, if the phase difference increases further, the PLL is locked again with the phase shifted by more than 180 degrees. This phenomenon is generally called a PLL slip. In a disk such as the CD-WO disk in which the data recording position is strictly determined according to the standard format, a phase error of even one clock (bit slip) causes failure in data recording.
Since writing of data is allowed only once in a CD-WO disk, if a bit slip occurs during recording of a CD-WO disk, a part or whole of the disk becomes unrecordable. For recording the same data again, recording must be made by using an unrecorded area of the disk or, alternatively, recording must be made from the beginning on a different disk. Since the difference in phase (position) between the ATIP data and the recorded data is not known during the recording operation, efficiency of data recording is rather poor and a disk is wasted.
It is, therefore, an object of the invention to provide an optical disk recording device to eliminate the above described disadvantage of the prior art optical disk recording device by providing an optical disk recording device capable of detecting a position error of recorded data by detecting, in real time, slip of a clock extracting PLL relative to read out ATIP data.